In many applicational areas, perfumes are used for masking malodors. Annoyance caused by malodors occurs frequently in daily life and impairs personal well-being. Such malodors are, for example, those resulting from substances transpired or excreted by humans, in particular, perspiration, mouth odors, feces and urine, odors caused by animal feces or urine, in particular, those of domestic pets, kitchen odors, such as those resulting from the preparation of onions, garlic, cabbage or fish, odors due to tobacco smoke, garbage, bathrooms, molds and waste.
In addition, malodors may be caused by many industrially produced basic materials used in cleansing agents, such as, for example, detergents and fabric softeners, or in body care products, such as, for example, soaps and cosmetics. The use of specific cosmetic preparations, such as, for example, hair dyes, hair-forming agents and depilatories, also produce malodors.
Many rubber and plastic products also produce malodors if, due to the method of their manufacture, they still contain quantities of highly odorous, volatile active ingredients. These malodors are usually caused by particularly odorous substances which are, however, generally only present in trace amounts. Such substances include, for example, nitrogen-containing compounds such as ammonia and amines, heterocyclic compounds such as pyridines, pyrazines, indoles, etc., and sulfur-containing compounds such as hydrogen sulfide, mercaptans, sulfides, etc.
The masking of malodors is a problem which is difficult to handle and solve with perfume compositions. Usually, it is only possible to mask malodors by means of a specially developed perfume oil having specific types of fragrances.
Malodor counteractings are particularly advantageous when they are capable of reducing the intensity of malodors without themselves possessing any significantly intense odor or fragrance. Such active ingredients do not mask malodors; rather, they neutralize the malodors. This has the advantage that, when using such active ingredients for perfuming objects or products having malodors, perfume oils of any desired type of fragrance can be used. The consumer can, therefore, be offered a considerably broader range of fragrance types for combating malodors.
In addition, active ingredients which neutralize malodors, provide the possibility of reducing the quantity of perfume oil previously required for masking odors. It is also possible to use less intensely odorous perfumes for combating malodors than those heretofore employed.
Another area in which malodor reducing compositions find utility is in breath freshening compositions such as chewing gum, mints, mouthwashes, lozenges and sprays. In addition to flavoring and perfuming ingredients which mask oral malodors, it is also useful to neutralize the ingredients which cause such malodors.
In recent years, a wide variety of substances have been proposed for use in neutralizing and/or suppressing malodors. These include certain acids such as undecylenic acid and a wide variety of esters, including esters of citric acid.
U.S. Pat. No. 6,495,097 describes the use of undecylenic acid and its lower alkyl esters as deodorants and odor neutralizers useful in a wide variety of compositions, perfumed and unperfumed. U.S. Pat. No. 4,010,253 discloses the use of certain esters of citric acid or acetylcitric acid in compositions for suppressing body odor. Citric acid itself has been used in personal deodorant compositions, as indicated in U.S. Pat. Nos. 5,098,694 and 5,662,937.
Recent patent literature disclosing the use of different classes of esters as malodor neutralizers include U.S. Pat. Nos. 7,157,411, 7,407,922 and 7,638,118, and Published Applications US 2010/0021413, US 2010/0028288 and US 2010/0034766.
Many of the esters disclosed in the prior art are quite effective in neutralizing malodors, and undecylenic acid (and its derivatives) has also shown some effectiveness in this area. It has now been discovered that combinations of undecylenic acid or citric acid and certain esters within particular molecular weight ranges have surprisingly shown synergistic effectiveness in neutralizing malodors.